1. Field of the Invention
The present application relates to a backlight unit for a liquid crystal display device, and more particularly, to a backlight unit having a dimming test portion and a method of driving the backlight unit.
2. Discussion of the Related Art
Liquid crystal display (LCD) devices having thin profiles, light weight, and low power consumption have been used in notebook computers, office automation devices, audio/video devices, and the like. Among the various types of LCD devices, active matrix LCD (AM-LCD) devices that employ switching elements and pixel electrodes arranged in a matrix structure are the subject of significant research and development because of their high resolution and superior suitability for displaying moving images. Thin film transistor LCD (TFT-LCD) devices use thin film transistors (TFTs) as the switching elements.
An LCD device includes a liquid crystal panel having switching elements and a backlight unit supplying light to the liquid crystal panel. A cold cathode fluorescent lamp (CCFL) has been used as a light source in the backlight unit. As the backlight unit is required to have a small size, a thin profile and a light weight, a light emitting diode (LED) having advantages in a power consumption, a weight and a brightness has been suggested as a light source for the backlight unit. In addition, a dimming test is performed for the LCD device to verify a normal operation of the LEDs in the backlight unit.
FIGS. 1 to 3 are views showing dimming tests for a backlight unit of a liquid crystal display device according to the related art.
In FIG. 1, a liquid crystal display (LCD) device 1 includes a control circuit part 5 and a backlight unit 10. The control circuit part 5 may be formed on a printed circuit board (PCB). The backlight unit 10 includes a plurality of light emitting diodes (LEDs) 16 and first and second inverter circuit parts 12 and 14. The control circuit part 5 supplies a dimming signal to first and second inverter circuit parts 12 and 14, and the first and second inverter circuit parts 12 and 14 control the plurality of LEDs 16 using the dimming signal, thereby performing a dimming test.
In FIG. 2, the LCD device 1 is connected to an external circuit 20 of a display system (not shown) such as a television set. The external circuit 20 supplies a dimming signal to the first and second inverter circuit parts 12 and 14, and the first and second inverter circuit parts 12 and 14 control the plurality of LEDs 16 using the dimming signal, thereby performing a dimming test.
In FIG. 3, the LCD device 1 is connected to a test apparatus 20. The test apparatus 20 supplies a dimming signal to the first and second inverter circuit parts 12 and 14, and the first and second inverter circuit parts 12 and 14 control the plurality of LEDs 16 using the dimming signal, thereby performing a dimming test.
In the dimming tests of FIGS. 1 to 2, since the backlight unit 10 receives the dimming signal from the control circuit part 5 of the LCD device 1 or the external circuit 20 of the display system, the dimming test is performed after the backlight unit 10 is assembled with the LCD device 1 or the display system. Accordingly, when abnormal operation of the LEDs 16 in the backlight unit 10 is detected through the dimming test, the LCD device 1 including the backlight unit 10 or the display system including the backlight unit 10 should be abolished or disassembled for rework. Further, in the dimming test of FIG. 3, an additional apparatus such as the test apparatus 20 is required, fabrication cost increases.